微信支付二维码Java代码

以下是微信支付二维码的Java代码示例：

import java.net.URLEncoder;
import java.util.SortedMap;
import java.util.TreeMap;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;

public class WeChatPayQRCode {

    private static final String CHARSET_UTF8 = "UTF-8";
    private static final String SIGN_TYPE_HMAC_SHA256 = "HMAC-SHA256";
    private static final String SIGN_TYPE_MD5 = "MD5";

    private static String createSign(SortedMap<String, String> parameters, String key, String signType)
            throws Exception {
        StringBuilder sb = new StringBuilder();
        for (String k : parameters.keySet()) {
            String v = parameters.get(k);
            if (v != null && !"".equals(v.trim()) && !"sign".equals(k) && !"key".equals(k)) {
                sb.append(k).append("=").append(v).append("&");
            }
        }
        sb.append("key=").append(key);
        if (SIGN_TYPE_MD5.equals(signType)) {
            return MD5(sb.toString()).toUpperCase();
        } else if (SIGN_TYPE_HMAC_SHA256.equals(signType)) {
            return HMACSHA256(sb.toString(), key);
        } else {
            throw new Exception(String.format("Invalid sign_type: %s", signType));
        }
    }

    private static String MD5(String data) throws Exception {
        java.security.MessageDigest md = java.security.MessageDigest.getInstance("MD5");
        byte[] array = md.digest(data.getBytes(CHARSET_UTF8));
        StringBuilder sb = new StringBuilder();
        for (byte item : array) {
            sb.append(Integer.toHexString((item & 0xFF) | 0x100).substring(1, 3));
        }
        return sb.toString();
    }

    private static String HMACSHA256(String data, String key) throws Exception {
        Mac sha256 = Mac.getInstance("HmacSHA256");
        SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes(CHARSET_UTF8), "HmacSHA256");
        sha256.init(secretKeySpec);
        byte[] array = sha256.doFinal(data.getBytes(CHARSET_UTF8));
        StringBuilder sb = new StringBuilder();
        for (byte item : array) {
            sb.append(Integer.toHexString((item & 0xFF) | 0x100).substring(1, 3));
        }
        return sb.toString().toUpperCase();
    }

    private static String buildQuery(SortedMap<String, String> parameters) throws Exception {
        StringBuilder sb = new StringBuilder();
        for (String k : parameters.keySet()) {
            String v = parameters.get(k);
            if (v != null && !"".equals(v.trim())) {
                sb.append(k).append("=").append(URLEncoder.encode(v, CHARSET_UTF8)).append("&");
            }
        }
        return sb.toString().substring(0, sb.length() - 1);
    }

    public static String generateQRCode(String appId, String mchId, String key, String body, String outTradeNo,
            int totalFee, String notifyUrl, String tradeType) throws Exception {
        SortedMap<String, String> parameters = new TreeMap<>();
        parameters.put("appid", appId);
        parameters.put("mch_id", mchId);
        parameters.put("nonce_str", java.util.UUID.randomUUID().toString().replace("-", ""));
        parameters.put("body", body);
        parameters.put("out_trade_no", outTradeNo);
        parameters.put("total_fee", String.valueOf(totalFee));
        parameters.put("spbill_create_ip", "127.0.0.1");
        parameters.put("notify_url", notifyUrl);
        parameters.put("trade_type", tradeType);
        parameters.put("product_id", outTradeNo); // NATIVE trade_type必填，商品ID
        String sign = createSign(parameters, key, SIGN_TYPE_MD5);
        parameters.put("sign", sign);
        String query = buildQuery(parameters);
        String url = String.format("weixin://wxpay/bizpayurl?%s", query);
        return url;
    }
}

使用示例：

String appId = "your_app_id";
String mchId = "your_mch_id";
String key = "your_key";
String body = "test";
String outTradeNo = "123456789";
int totalFee = 100;
String notifyUrl = "http://your.notify.url";
String tradeType = "NATIVE";
String qrCodeUrl = WeChatPayQRCode.generateQRCode(appId, mchId, key, body, outTradeNo, totalFee, notifyUrl, tradeType);

注意，为了使用该代码，你需要引入 Apache Commons Codec 依赖包。可以在 Maven 中添加以下代码：

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.15</version>
</dependency>